It is known in the art for a flexible circuit wiring board have circuit wiring conductors outwardly protruding in the form of finger leads. An example of such a prior art circuit board is shown in FIGS. 3 and 4. In the circuit board of FIGS. 3 and 4, the protruding circuit wiring conductors 11 are composed of rolled copper or electrolytic copper and may be called TAB leads. These TAB leads extend beyond the edge of an aperture or window 12 that is formed in a flexible insulating base member 13 for connection to a device, i.e., an electrical circuit component.
In the above-mentioned flexible circuit wiring board of conventional structure, the circuit wiring conductors 11 must be so strong that the inner leads protruding into the aperture 12 will not be easily deformed. Because of this reason, it is not allowed to finely form the circuit wiring conductors 11 i.e., high contact density is not possible.
In order to solve such a problem, it can be contrived to form the circuit wiring conductors 11 using an indium-copper alloy or the like instead of a traditional material such as rolled copper or electrolytic copper. This method, however, is not desirable since it impairs flexibility of the flexible circuit wiring board.